This invention relates to control of current transients in power-up or power-down of one or more electrical devices.
When an electrical device is powered up or powered down, a current transient, reflecting an in-rush or other rapid change of current through one or more components of the device, often appears. This current is potentially damaging to the device, and the total current transient that must be initially delivered is often excessive. What is needed is an approach that limits or redistributes, or staggers the occurrence of, transient current within two or more selected device subsets so that (1) no component is likely to be damaged as a result of such current and (2) the amount of transient current required at any time is modest. Preferably, the approach should allow simultaneous or sequential delivery of current within any subset.
These needs are met by the invention, which sequentially supplies in-rush current to each of a plurality of electrical devices so that, at any time, only a limited number of devices experience a current transient (e.g., in-rush current) and only a limited amount of such current is delivered to any one device. In one embodiment, where two or more devices are to be powered up (or down) at approximately the same time, the devices are allocated to one or more mutually exclusive subsets of devices, and each subset of devices is powered up (or down) with a different associated time delay, or with a sequence of differing time delays within that subset. A current transient time interval associated with a first subset, during which all devices in the first subset are powered up, simultaneously or sequentially, overlaps insubstantially, or not at all, with a current transient time interval associated with a second subset, through incorporation of a time delay between power-up (or power-down) in any two consecutive device subsets.